The present invention pertains to welding tools and, more particularly, to a hand held backing tool for use in the repair of holes in sheet metal panels.
In repairing holes in sheet metal panels by welding, particularly thin metal automotive body panels, only a relatively thin layer of weld metal is required. However, the hole to be filled must be backed with a large metal patch or with some type of plate which is held in place until the welding process is completed. If a patch is used, the weld metal adheres to it as well as to the edge of the hole and the patch becomes a permanent part of the repair. If a plate is used, it must have a surface which conforms to the inside surface of the panel to be repaired and covers the hole therein. In addition, the plate must be attached or held in a manner to maintain it in position while the welding process is carried out. It is known in the prior art to hold a piece of metal against the backside of a hole in a panel to be closed by welding. However, finding a piece of metal of the right size and shape and comprising a material to which the weld metal will not adhere is often difficult. In addition, positioning and holding the piece of metal is often cumbersome and tedious. The wide variety of hole shapes and sizes and body panel contours encountered in auto body repair simply compounds the problems associated with the use of metal backing members.
U.S. Pat. No. 2,584,072 shows a backup plate which is demountably attached to the panel to be repaired by a magnet which spans the hole. However, this device does not lend itself well to easy repositioning as the hole is filled, for example, along an elongated crack or the like. In addition, although backing plates of different shapes are disclosed along with magnets of corresponding varying shapes, to provide complete assemblies to accommodate a wide variety of auto body panel contours would be prohibitively expensive.
U.S. Pat. No. 3,273,881 discloses a welding device for the repair of auto body panels which assists in positioning and initially holding a permanent backing patch until it can be tacked in position. As previously indicated, the patch becomes a permanent part of the repair.
U.S. Pat. No. 2,449,371 shows a hand operated backing tool for positioning a backing plate along the portion of the inside cylindrical surfaces of two pipe ends to be joined by a continuous welded seam. The tool is particularly constructed for use with pipe ends spaced axially apart so the backing plate can be inserted through the gap between the ends, moved progressively around the circumference of the pipe ends as the weld bead is laid down, and removed from the gap before the seam is fully completed. This tool is essentially a single purpose device with limited utility.
U.S. Pat. No. 1,902,051 also shows a backing plate holder for use in welding circular pipe sections. The device is intended to be secured in position inside the pipe and is adapted for use in making either circumferential or axial welded seams.
There remains a real need in the welding art, particularly in the auto body repair industry, for a simple weld backing plate device which is convenient to use, readily adaptable or convertible to varying auto body panel contours and hole sizes, and of relatively inexpensive construction.